Hogan-Howe is on collision course with the Conservative government that selected him.
Photograph: David Fisher/Rex Features

Britain’s most senior police officer has directly challenged the government, warning that planned funding cuts are so large they would endanger the safety of the public.

Sir Bernard Hogan-Howe, the commissioner of the Metropolitan police, said his force would have to shrink, damaging its ability to respond to a terrorist attack or a repeat of the 2011 riots across London.

Hogan-Howe is now on a collision course with the Conservative government that selected him in 2011. He has been pondering when to make his intervention to rally support against the scale of government cuts, and said on Wednesday they would see the Met lose £1bn by 2020 and shrink to levels last seen in the 1970s.

In an interview with the London Evening Standard, Hogan-Howe said: “It’s a lot of money and a massive change and as a result of that, I genuinely worry about the safety of London. We think we can expect to lose somewhere between 5,000 to 8,000 police officers.”

The Met, which is Britain’s largest force, was expecting to have to save £800m by 2020 because of government funding cuts. But late last week it found out it may have to lose another £180m because of a Home Office change in the way money is shared among the forces across England and Wales.

Hogan-Howe said: “We are having to face today’s and tomorrow’s challenges with resources going back to the 1970s. That’s when London had a population of around six million, today we are 8.6 million and we believe it will rise to about nine million in 2020.”

They say between 2010 to 2015 they cut the cost to the taxpayer of policing, cut crime and also reformed the police.

The commissioner challenges the criticism in his intervention. “For the past four years, we have taken cuts in budget and we have just got on with it. We have not waved shrouds – we are the only force to have kept police officer numbers up – today they stand at about 31,800.”

Hogan-Howe’s warning on terrorism, for which the Met is the national lead, is also stark: “Should we get a roaming firearms attack, could we deal with it? With a smaller force, can we maintain firearms ability?”

He said policing in London, which carries special risks as it is the capital city, would be less visible, and officers may take longer to reach certain incidents: “We would have to ‘reprofile’ neighbourhood policing; we have got to get to emergencies and I would want to have some neighbourhood policing everywhere.

“It will get pretty twitchy in terms of coverage of London. There would be less visibility. There would be less of it in the neighbourhoods and in our response section. There is no doubt that we would be slower.”

Police forces will find out later this year how much their budgets will be cut when the Treasury decides how much money each government department will get. They are braced for cuts of 25% to 40% and, nationally, chiefs expect at least 22,000 officers to go even if the cuts are at the lower end.

The Home Office’s plans to change the way money is shared out among forces has already led to the Lancashire force saying it will lose so much money it may be rendered unviable. The Met is earmarked to lose more than 10% of its government grant, on top of the minimum cut of 25% it was already expecting, with that money going to smaller forces.

Hogan-Howe was the choice in 2011 of Theresa May, in her role as home secretary, and the Tory mayor of London, Boris Johnson. Selection panels rated government critic Sir Hugh Orde as a better choice, despite Hogan-Howe’s crime-cutting record while chief constable of Merseyside. The Conservatives picked Hogan-Howe believing he would not turn into a vocal critic in the same way Orde had become.

Hogan-Howe’s tenure has seen overall crime fall, and he is expected to have his five-year contract, due to run out next year, extended by two years. Insiders say he is shrewd politically and it remains to see how his vocal and now unequivocal criticism will affect his relationship with government.

Responding to Hogan-Howe’s comments, Mike Penning, the minister for policing, said: “There is no question that the police still have the resources to do their important work. As HMIC [Her Majesty’s Inspectorate of Constabulary] has shown, what matters is how officers are deployed, not how many of them there are in total.”

One possible reason for the timing of the commissioner’s critical comments is the launch on Thursday of a report about the future of safety in London which gives him intellectual cover.

The report is by the Royal Society of Arts, whose work on reforming the Police Federation was backed by May’s Home Office. The report warns budget cuts and changes in London mean that “the next decade will be amongst the most challenging in the Met’s history”. It says the public sector in the capital must be reformed to keep its people safe.